docs: def imt2tup(string):
      """
      >>> imt2tup('PGA')
      ('PGA',)
      >>> imt2tup('SA(1.0)')
      ('SA', 1.0)
      >>> imt2tup('SA(1)')
      ('SA', 1.0)
      """
      s = string.strip()
      if not s.endswith(')'):
          # no parenthesis, PGA is considered the same as PGA()
          return (s,)
      name, rest = s.split('(', 1)
      return (name,) + tuple(float(x) for x in ast.literal_eval(rest[:-1] + ','))